Nitrogen fixation by bacteria requires the enzyme:

Options

A. decarboxylase
B. nitrogenase
C. nitrogen deaminase
D. nitrodioxidase

Answer

To solve the question "Nitrogen fixation by bacteria requires the enzyme:", we will follow these steps:

### Step-by-Step Solution:

1. **Understand the Process of Nitrogen Fixation**:
- Nitrogen fixation is the process through which atmospheric nitrogen (N₂) is converted into ammonia (NH₃) or related compounds in soil and water. This process is essential for making nitrogen available to living organisms, particularly plants.

2. **Identify the Role of Bacteria in Nitrogen Fixation**:
- Certain bacteria, including cyanobacteria and some soil bacteria, are capable of fixing nitrogen. They play a crucial role in converting inert atmospheric nitrogen into a form that can be utilized by plants.

3. **Recognize the Enzymes Involved**:
- The key enzyme involved in nitrogen fixation is known as nitrogenase. This enzyme facilitates the reaction that converts nitrogen gas into ammonia.

4. **Evaluate the Given Options**:
- Option 1: Decarboxylase - This enzyme is involved in the removal of a carboxyl group from a molecule, not nitrogen fixation.
- Option 2: Nitrogenase - This is the enzyme that catalyzes the conversion of nitrogen gas to ammonia.
- Option 3: Nitrogen deaminase - This enzyme is involved in the removal of an amino group from amino acids, not directly related to nitrogen fixation.
- Option 4: Nitrodioxidase - This is not a recognized enzyme related to nitrogen fixation.

5. **Select the Correct Answer**:
- Based on the understanding that nitrogenase is the specific enzyme responsible for nitrogen fixation, the correct answer is **Option 2: Nitrogenase**.

### Final Answer:
Nitrogen fixation by bacteria requires the enzyme **nitrogenase**.

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